It is a positive Torah commandment to eliminate all ĥametz from our possession before Pesaĥ, as it is written, “Yet on the first day you must remove the se’or from your homes” (Shemot 12:15). The oral tradition teaches that we are to clear out the ĥametz by midday of the fourteenth of Nisan, Erev Pesaĥ. This ruling is supported by the verse, “You shall not slaughter the blood of My sacrifice over ĥametz” (ibid. 34:25), which is interpreted to mean that one may not slaughter the Paschal sacrifice while there is still ĥametz in his possession, and the time for slaughtering the Paschal sacrifice begins at midday on the fourteenth of Nisan (see Pesaĥim 4b; MT, Laws of Ĥametz 2:1). Men and women are equally obligated in this mitzva, as they are concerning all of the mitzvot of Pesaĥ.
Whoever did not remove the ĥametz from his home by midday of the fourteenth of Nisan is in violation – every single moment that he delays – of the positive commandment of removing the ĥametz (MB 443:1). Furthermore, from the moment the Pesaĥ holiday begins, he is in violation of two prohibitions: bal yimatzei, as it is written, “Seven days there shall be no se’or found in your homes” (Shemot 12:19), and bal yera’eh, as the Torah declares, “Matzot shall be eaten seven days; and no ĥametz of yours shall be seen, and no se’or of yours shall be seen within all your borders” (ibid. 13:7). Thus, by fulfilling the mitzva of getting rid of the ĥametz we are saved from two prohibitions: bal yera’eh and bal yimatzei – that ĥametz should be neither seen nor found in our possession.
The mitzva of removing the ĥametz is the first in a series of mitzvot connected with Pesaĥ. As noted, ĥametz on Pesaĥ is a metaphor for the evil inclination, and one has to clear out the ĥametz from the house in order to experience the sanctity of the Pesaĥ sacrifice and the eating of the matza properly. Therefore, the first of the preparations for Pesaĥ is removal of the ĥametz.
. Let us summarize the opinions regarding the times of the onset of the ĥametz prohibitions. The removal and destruction of the ĥametz must be done by midday of the fourteenth (perhaps according to Ha-ma’or the mitzva begins at midday, but according to the rest of the Rishonim, on the Torah level the removal and destruction of the ĥametz must be completed by midday). There is a dispute regarding the starting times of the other mitzvot connected to ĥametz. Regarding the prohibition of eating ĥametz, R. Yehuda maintains that the prohibition begins at midday of the fourteenth, and R. Shimon maintains that the prohibition of eating ĥametz, on the biblical level, begins at the onset of the Pesaĥ festival. Most Rishonim adopt the view of R. Yehuda that the eating prohibition begins at midday of the fourteenth, but there are those who adopt the view of R. Shimon that the eating prohibition begins at the start of the holiday. Regarding the prohibitions of bal yeira’eh and bal yimatzei, most Rishonim are of the opinion that these prohibitions begin at the onset of the Pesaĥ festival, while a minority hold that these prohibitions begin at midday of the fourteenth.
Additionally, note that one who participated in the Paschal sacrifice (korban Pesaĥ) while he still had at least a kezayit of ĥametz in his possession, violated a Torah prohibition, as it says: “You shall not slaughter the blood of My sacrifice over ĥametz” (Shemot 34:25). If he was warned about this and still did it on purpose, he incurs the penalty of lashes (MT, Laws of Korban Pesaĥ 1:5).